package 编程题;
//客似云来

import java.util.Scanner;
public class Num_8_2_02 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNextInt()) {// 注意，如果输入是多个测试用例，请通过while循环处理多个测试用例
            int from = sc.nextInt();
            int to = sc.nextInt();

            long[] fb = new long[81];
            fb[1] = 1;
            fb[2] = 1;
            long sum = 0;
            for(int i = 3; i <= to; i++ ){
                fb[i] = fb[i - 1] + fb[i - 2];

            }

            for(int i = from; i <= to; i++ ){
                sum += fb[i];
            }


            System.out.println( sum );
        }
    }
}